In recent years, voice over IP (VoIP) has become a new standard for voice communications due to the ubiquity of Internet Protocol (IP) networks. Compared with traditional telephonic technology, VoIP offers the benefits of cost savings, open standards, multi-vendor interoperability, and integrated voice and data networks. Other real-time applications include, for example, video-conferencing, multimedia streaming and other multimedia services that require guaranteed quality of service (QoS), all of which may benefit from the technique for end-to-end admission control of real-time packet flows in accordance with the present invention.
Compared with traditional telephonic technology, VoIP also has its own difficulties. Traditionally voice communications have been carried over the public switched telephone network (PSTN), a circuit-switched network that can ensure the quality of each call through dedicated bandwidth allocations. This consistently high level of voice quality is called “toll quality.” Unlike PSTN, IP networks are based on packet switching rather than circuit switching. Packet switching works well for data communications because it maximizes bandwidth utilization by allowing all users to dynamically share network bandwidth. However, traditional packet switching techniques do not adequately recognize the mixing of many different applications that have different traffic flow characteristics and performance requirements in one network or link. For example, real-time applications typically require minimum delay, low packet loss (or guaranteed bandwidth), whereas non-real-time application may be able to tolerate longer delays and recover from packet loss. Though telephony service, video-conferencing and one-way multimedia streaming are real-time applications, the last two are more bandwidth-demanding.
Some providers employ bandwidth management techniques such as prioritization to ensure that VoIP and other real-time multimedia applications get what they need. However, bandwidth management alone simply allocates bandwidth to critical applications at the expense of other applications and does not limit or prevent real-time applications from congesting a link to a point where the performance or quality of service offered for all real-time flows become unacceptable. Some providers or enterprises over-provision their network capacity so that application demands would never hit the bandwidth limit. This solution is not economical since it may require expensive upgrades to the carrier networks to meet the increasing peak demands for bandwidth. None of the existing solutions can prevent network congestion in an efficient and cost-effective manner and still provide high quality of service for real-time flows.
In view of the foregoing, it would be desirable to provide a solution which overcomes the above-described inadequacies and shortcomings.